1. Field of the Invention
The present invention relates to a semiconductor laser control apparatus, more particularly, to a semiconductor laser control apparatus for confirming the service life of a semiconductor laser by detecting the current increase of the semiconductor laser from an initial state thereof.
2. Description of the Related Art
Recently, bar codes have been used in various industrial fields as represented by point-of-sale (POS) systems employed in distribution businesses to provide bar code readers with compact, inexpensive and with low power consumption features. Semiconductor lasers have mainly been used for POS systems rather than gas lasers.
However, the service life of a semiconductor laser is relatively short, and when the POS system becomes inoperatable because of expiration of the service life, the operation performed by the POS system stops. Note, the service life of the semiconductor laser varies greatly with the individual semiconductor laser, and further the service life of the semiconductor laser varies greatly with the conditions (especially, temperature) of the POS system using the semiconductor laser. Concretely, the service life of a semiconductor laser is, for example, 4000.about.7000 hours under continuous operation at 50.degree. C., but the service life of the same semiconductor laser is, for example, two times higher (8000.about.14000 hour under continuous operation at 40.degree. C.
Therefore, it has been desired to make it possible to replace the semiconductor laser by predicting the expiration of its service life before a failure of operation and to extend the time of operation until such inactivity. Note, as described above, the service life of the semiconductor laser varies greatly with the individual semiconductor laser and the temperature of the POS system using the semiconductor laser.
Note, the configuration of a semiconductor laser control apparatus to prolong the service life thereof is proposed by some inventors including the inventors (the same applicant, or asignee) of this application under Japanese Patent Application NO. 02-314606 (which corresponds to U.S. patent application No. 07/794,226). Further, an example of the POS system, or a bar code reader using the semiconductor laser control apparatus is also described in JPPA,606.